Rethink this one
First of all, the engines are nearly impossible to get parts for. The fuel burns are outrageous and the avionics will not be compliant with EASA requirements without great expense. Here in the US, we commonly refer to GIIs as "geranium planters". GIIIs are nearly in the same boat. The least expensive Gulfstream that is reasonably operationally efficient is a later GIV SP. The best "bang for the buck" is a GV. They go for about $20 mil and have reasonably upgradeable avionics and decent fuel burns. Anything that you spend on a GII is a total write off in very short order.